As with garden plants there are macronutrients - nitrogen, potassium and phosphorus - and micronutrients. Aquarium plants get their macronutrients from the ammonia made by the fish (nitrogen) and from fish food (potassium, phosphorus) but they also need these trace element micronutrients. One of the best sources of these micronutirents is Seachem Flourish Comprehensive Supplement for the Planted Tank.